While most people do intermittent fasting to lose weight, research from the National Institute on Aging (NIA) suggests that intermittent fasting can also improve brain functioning, and help maintain lean muscle mass.

Mattson and his team conducted studies on animals with Alzheimer-like conditions, and found that alternating between days of fasting and normal eating seemed to slow or even reverse brain impairment, as Celebrity Health Fitness has reported.

Intermittent fasting also helped the animals maintain their lean muscle mass even as they aged — the exact opposite of what happens to both animals and people as they get older.

Similar experiments conducted on humans (alternating between days of normal eating and calorie restriction) showed the same effects.

Dr. Mattson said fasting for short periods of time like 16 to 24 hours induces a state of stress in the body, which responds by releasing neurotrophic proteins that stimulate neurons and other cells.

A major advantage of intermittent fasting is that it’s easier to maintain than a linear diet where you’re restricting yourself all the time. In the alternate-day fasting model, people ate whatever they wanted on non-fasting days and then ate a low-calorie diet (about 500 calories a day) on fasting days.

Intermittent fasting has skyrocketed in popularity, thanks to the runaway success of the Fast Diet (or 5:2 diet), which calls for fasting (500 calories a day) for two days of the week and eating whatever you want the other five days.

Another popular intermittent fasting diet is the Every Other Day Diet, where you alternate every other day between fasting and regular eating. Thousands of people say they lost dramatic amounts of weight quickly on both of these IF regimes.

Not only do most people lose weight quickly on these plans, but they say it’s easier to stick to their diets. “We think that once the people get adjusted to the diet, it is easy to adhere to,” said Dr. Mattson. “If you know that tomorrow you can eat normally, you can make it through today.”

Jackman said IF also gave him more energy and improved his sleep. Jackman said he was inspired to follow intermittent fasting after reading The 8-Hour Diet by David Zinczenko, the former editor-in-chief of Men’s Health.

Hugh’s 16/8 intermittent fasting protocol involves doing all his eating for the day during an eight-hour window and then not eating at all (except for water) for 16 hours.

Jackman typically consumes all his calories between 10 am and 6 pm. It’s an eating plan he follows even when he’s not training for a role.

Research indicates that periodic fasting also dramatically increases human growth hormone. Reps from the Intermountain Medical Center Heart Institute said men who fasted for 24 hours experienced a 2,000% spike in HGH, while women saw a 1,300% increase. Studies show fasting also stabilizes blood sugar and improves cholesterol.